Notes on the Birds of the Diep River and Riet Vlei

Long-term physical, chemical and biological changes in a small, urban estuary

“…A fairly anecdotal account of the composition of the bird fauna in the 1950s is provided by Scott (1954) and this can be compared with recent counts on the website http://cwac.adu.org.za (Animal Demography Unit Coordinated Waterbird Counts [CWAC] project). Although these data are difficult to compare statistically, given differences in frequency and intensity of observation, they do suggest an increase in bird numbers, as has been observed in Rietvlei.…”

“…Although these data are difficult to compare statistically, given differences in frequency and intensity of observation, they do suggest an increase in bird numbers, as has been observed in Rietvlei. For example, Scott (1954) gave the following maximum bird densities for abundant resident species (each followed by recent maximum CWAC counts in brackets) -kelp gull: 'up to 50' (116); Hartlaub's gull: 'up to 70' (136); common tern: '40-50' (250); cormorants: '<12' (82, for summed species); Cape shoveller: 'a few' (20). Other species absent from Scott's (1954) account are also now common, most notably red-knobbed coot and African darter, which are predominantly freshwater species.…”

“…For example, Scott (1954) gave the following maximum bird densities for abundant resident species (each followed by recent maximum CWAC counts in brackets) -kelp gull: 'up to 50' (116); Hartlaub's gull: 'up to 70' (136); common tern: '40-50' (250); cormorants: '<12' (82, for summed species); Cape shoveller: 'a few' (20). Other species absent from Scott's (1954) account are also now common, most notably red-knobbed coot and African darter, which are predominantly freshwater species. All these data thus support the conclusion that the estuary now supports higher numbers and more species of birds than in the past.…”

“…Millard and Scott (1954) provided the first biological survey of the system, while Scott (1954) published a short descriptive account of the bird fauna. Since then, Weil (unpublished data) carried out an ecological survey of the lagoon section only in 1974, duplicating the methods of Millard and Scott (1954).…”